If what you say is true, that creasing in Sub-D just changes the way the geometry displays in that mode without actually changing it, then I guess I'm confused.

What is the best way to create a Poly object, convert to SD for cleanup, convert back to Poly and retain the same sharp lines as I had in SD mode?

Or follow-up question would be what would be the reasoning to convert back to Poly after a good SD edit...texturing? Can you texture in SD?